1, Field of the Invention
The present invention relates to a linear roller contact bearing assembly comprising at least one pair of elongate support means including a first and a second elongate support member, said two support members being displaceable relative to each other in the direction of their longitudinal extension. One of the first and second elongate support members may be part of a fixed supporting structure on which is mounted either one longitudinally movable support member or several telescopically extensible support members. For instance, the support members movable relative to each other can be part of the supporting structure of a table used for X-ray diagnosis. In this case, usually several table portions have to be movably supported by the supporting structure and, further, have to be extensible in both directions.
This and other applications require that the linear roller contact bearing assembly, on the one hand, has a height dimension as small as possible and, on the other hand, presents a smooth and precise running behaviour in every position of displacement and in every load condition such that the rigidity of the supporting structure is not impaired by the movable arrangement of its elements.
2, Prior Art
A linear roller contact bearing assembly of the kind mentioned above is disclosed in Swiss Patent No. 568,502. Thereby, the rolling members are guided in rod-like members which are offered in different lengths and are intended to be freely movably mounted between the tracks. Such roller contact bearing rods have the disadvantages that they can support the support members movable relative to each other in longitudinal direction only along a part of their length in any displacement position, and that the rolling members more and more drift away, thereby continuously limiting the theoretically available path of displacement.
Another similar linear roller contact bearing assembly of the kind mentioned above is disclosed in Swiss Patent No. 505,311. This assembly is a ready-to-mount unit, similar to the roller or ball bearings for rotational movement. Because they are finally assembled and in a condition to be be readily used, such linear roller contact bearing assemblies have quite a large height. In order to reliably support a longitudinally extending support member to be able to be longitudinally displaceable, one would require a plurality of such assemblies distributed along the extension of the support member. However, a design incorporating a plurality of supporting assemblies has the disadvantage that the ends of a continuous support member leave the bearing assembly at certain positions and have to be inserted therein again. The inserting operation is difficult due to a possible bending of the support members. Even if additional guiding elements are provided, the alignment of the support member in a loaded condition is hardly possible. It is believed that a precise guiding and supporting and a smooth movability of the support member is practically impossible with a bearing assembly of this kind.